Russian President Vladimir Putin told military personnel gathered at the Kremlin on Friday that recent events in Crimea were "a serious test" for the Russian military.

He said the professionalism of the Russian military "helped ensure peaceful conditions" for the Crimea referendum.

Defence Minister Sergei Shoigu told Mr Putin that all Ukrainian service personnel loyal to Kiev had left Crimea.

Russian news agencies reported that Moscow would hand Kiev any military equipment left in Crimea by Ukrainian units that had left the peninsula.

'Huge build-up'

Nato Secretary-General Anders Fogh Rasmussen said the organisation was extremely worried about a "huge military build-up" on Ukraine's borders.

He said Nato had plans in place to ensure effective defence and protection for all its members, including the three Baltic states - Estonia, Latvia and Lithuania.

Mr Obama, in his interview recorded before he left Europe on Thursday, said President Vladimir Putin had been "willing to show a deeply-held grievance about what he considers to be the loss of the Soviet Union".

But he warned that the Russian leader should not "revert back to the kinds of practices that were so prevalent during the Cold War".

'Putin misreading US'

"I think there's a strong sense of Russian nationalism and a sense that somehow the West has taken advantage of Russia in the past, " Mr Obama said. "What I have repeatedly said is that he may be entirely misreading the West. He's certainly misreading American foreign policy."

Mr Obama said the US has "no interest in circling Russia" and "no interest in Ukraine beyond letting Ukrainian people make their own decisions about their own lives".

Media captionSteve Rosenberg ponders Russia's next move following the annexation of Crimea

Earlier, ousted Ukrainian President Viktor Yanukovych, who fled to Russia last month, called for a national referendum to determine each region's "status within Ukraine".

He was replaced after massive demonstrations and clashes between protesters and police in which more than 100 people died. The Kremlin says the new government in Kiev came to power illegally.

Ukraine's former Prime Minister Yulia Tymoshenko, who has announced that she will run for president in May's elections, said on Friday that she was sure Mr Yanukovych would stand trial one day for calling for the country to be broken up.

"If these really are his words, then this once again proves that the person who was once the president of Ukraine has effectively turned into a tool used for Ukraine's destruction," Ms Tymoshenko told reporters.

Ukraine is not a member of Nato and would not be covered by the collective defence agreement in the Nato treaty.

The organisation has already announced enhanced air policing over the three Baltic states - the only countries formerly part of the Soviet Union which are now Nato members.